Grant channel assignment

ABSTRACT

Methods and apparatus for scheduling grant channels to carry grant messages to a plurality of scheduled mobile stations. The scheduling of grant channels involves dynamically assigning to a current mobile station of the plurality of scheduled mobile stations, a previously unassigned grant channel from a list of grant channels monitored by the current mobile station. If there are more mobile stations to be processed in the plurality of scheduled mobile stations, then the scheduling moves to a next mobile station in the plurality of scheduled mobile stations, and the assignment process is repeated. Furthermore, if not every grant channel has been assigned a mobile station, then the order of the plurality of scheduled mobile stations is rearranged, and the assignment and the movement processes are repeated.

CLAIM OF PRIORITY UNDER 35 U.S.C. §119

[0001] The present Application for patent claims priority to ProvisionalApplication No. 60/463,414 entitled “Grant Channel Assignment” filedApr. 15, 2003, and assigned to the assignee hereof and hereby expresslyincorporated by reference herein.

BACKGROUND

[0002] 1. Field

[0003] The disclosed embodiments relate generally to telecommunicationnetworks, and more specifically to assigning grant channels to mobilestations in such networks.

[0004] 2. Background

[0005] A High Data Rate (HDR) subscriber station or mobile station (MS),referred to herein as an access terminal, may be mobile or stationary,and may communicate with one or more HDR base stations (BS), referred toherein as modem pool transceivers. An access terminal transmits andreceives data packets through one or more modem pool transceivers to anHDR base station controller, referred to herein as a modem poolcontroller. Modem pool transceivers and modem pool controllers are partsof a network called an access network. An access network transports datapackets between multiple access terminals. The access network may befurther connected to additional networks outside the access network,such as a corporate intranet or the Internet, and may transport datapackets between each access terminal and such outside networks. Anaccess terminal that has established an active traffic channelconnection with one or more modem pool transceivers is called an activeaccess terminal, and is said to be in a traffic state. An accessterminal that is in the process of establishing an active trafficchannel connection with one or more modem pool transceivers is said tobe in a connection setup state. An access terminal may be any datadevice that communicates through a wireless channel or through a wiredchannel, for example using fiber optic or coaxial cables. An accessterminal may further be any of a number of types of devices includingbut not limited to PC card, compact flash, external or internal modem,or wireless or wireline phone. The communication link through which theaccess terminal sends signals to the modem pool transceiver is called areverse link. The communication link through which a modem pooltransceiver sends signals to an access terminal is called a forwardlink.

[0006] In various system configurations of the HDR access network, thebase station (BS) may use individual Grant Channels (GCH) to issuemobile station (MS)-specific grants, such as Reverse EnhancedSupplemental Channel (R-ESCH) grants. According to these systemconfigurations, an individual GCH may carry information for a single MSonly. Thus, if more than one MS needs to be scheduled simultaneously ina particular time slot, then more than one GCH must be used. The numberof grant channels used is determined by the number of mobile stationsthat can be simultaneously scheduled in the same time slot, and also bythe existence of a common grant channel.

[0007] Accordingly, to ensure mobile stations are notified about thegrants, each mobile station can monitor every individual one of thegrant channels. In that case, as long as the number of mobile stationsscheduled in a time slot does not exceed the number of grant channels,each scheduled mobile station can be notified about the grant. Thismonitoring of every individual grant channel, however, requires eachmobile station to monitor a relatively large number of parallel codechannels, and increases the complexity of the mobile station processing.To reduce the required processing in the mobile stations, a subset ofthe grant channels can be assigned to each mobile station formonitoring. However, requiring the mobile station to monitor only asubset of the grant channels means that there may be times when notevery scheduled mobile station can be notified about the grant. Thisexpected performance loss, comprising the failure of GCH notification,is referred to herein as a “GCH outage” and is due to conflicts betweenthe assigned subsets.

[0008] It should be apparent from the discussion above that there is aneed for efficient notification of grant channels to each mobile stationsuch that each mobile station monitors less than all availableindividual grant channels. The present invention satisfies this need.

SUMMARY

[0009] Embodiments disclosed herein efficiently assign grant channels tomobile stations such that each mobile station monitors less than allavailable individual grant channels. The assignment of grant channels tomobile stations includes selection of a grant channel to carry thenotification to each scheduled mobile station.

[0010] In one aspect, grant channels are scheduled to carry grantmessages to a plurality of scheduled mobile stations. In particular, thescheduling of grant channels involves dynamically assigning, to acurrent mobile station of the plurality of scheduled mobile stations, apreviously unassigned grant channel from a list of grant channelsmonitored by the current mobile station. After scheduling the currentmobile station, if there are more mobile stations to be processed in theplurality of scheduled mobile stations, then the scheduling moves to anext mobile station in the plurality of scheduled mobile stations, andthe assignment process is repeated. Furthermore, if not every grantchannel has been assigned to a mobile station, then the order of theplurality of scheduled mobile stations is rearranged, and the assignmentand the movement processes are repeated.

[0011] In another aspect, scheduling grant channels to mobile stationsfurther includes statically assigning at least one grant channel to eachmobile station to monitor. In one embodiment, the static assignmentinvolves assigning each of a first plurality of mobile stations to oneof the grant channels in order until all available grant channels havebeen assigned, where the first plurality of mobile stations is a subsetof a total number of mobile stations operating within an area of theCDMA communications network. The static assignment also involvesassigning the remainder of the mobile stations to a first same number ofgrant channels, in order. In another embodiment, the static assignmentinvolves randomly selecting a set of grant channels from the monitoredgrant channels to assign to each mobile station to monitor.

[0012] In another aspect, a CDMA communications network having a basestation and a plurality of mobile stations includes a base station witha controller configured to schedule grant channels that carry grantmessages to a plurality of scheduled mobile stations. The controllerincludes a grant channel assignment module that operates to assign, to acurrent mobile station of the plurality of scheduled mobile stations, apreviously unassigned grant channel from a list of grant channelsmonitored by the current mobile station. The base station also includesa modulator configured to process and spread the grant messages. Thebase station further includes a transmitter unit configured to conditionthe processed grant messages, to generate a forward link signal, and totransmit the forward link signal on grant channels.

[0013] Other features and advantages of the present invention should beapparent from the following descriptions of the exemplary embodiments,which illustrate, by way of example, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 illustrates an exemplary configuration of assigning grantchannels to mobile stations.

[0015]FIG. 2A, FIG. 2B, and FIG. 2C illustrate an exemplary “dynamic”process in which a grant channel is selected or assigned to carry agrant message to a scheduled mobile station.

[0016]FIG. 3 summarizes a “greedy” technique applied in the exemplarydynamic selection process described in FIG. 2A, FIG. 2B, and FIG. 2C.

[0017]FIG. 4 illustrates simulation results of exemplary grant channelassignment performance expressed in terms of a relative reverse linkefficiency where the number of mobile stations scheduled per time slotis uniformly distributed over {1, 2, . . . , k}.

[0018]FIG. 5 illustrates simulation results of exemplary grant channelassignment performance expressed in terms of a relative reverse linkefficiency where the number of mobile stations scheduled per time slotis distributed according to the following probability distribution:P(0), P(1), . . . , P(8)={0.00860689, 0.0458367, 0.172538, 0.303443,0.269816, 0.138511, 0.0490392, 0.0104083, 0.00180144}.

[0019]FIG. 6 is a simplified block diagram of a CDMA communicationsystem, such as the HDR access network.

DETAILED DESCRIPTION

[0020] The detailed description set forth below in connection with theappended drawings is intended as a description of exemplary embodimentsof the present invention and is not intended to represent the onlyembodiments in which the present invention can be practiced. The term“exemplary” used throughout this description means “serving as anexample, instance, or illustration,” and should not necessarily beconstrued as preferred or advantageous over other embodiments. Thedetailed description includes specific details for the purpose ofproviding a thorough understanding of the present invention. However, itwill be apparent to those skilled in the art that the present inventionmay be practiced without these specific details. In some instances,well-known structures and devices are shown in the drawing figures inblock diagram form to avoid obscuring the concepts of the presentinvention. In the drawing figures, like reference numerals refer to likestructures.

[0021] As described above, when only a subset of the grant channels isassigned to each mobile station to monitor, there may be times when notevery scheduled mobile station can be notified about the grant. Thisexpected performance loss (i.e., the “GCH outage”) due to conflictsbetween the assigned subsets is undesirable. As described herein, it canbe shown that the expected performance loss due to this “GCH outage” isnot significant as long as each mobile station is able to monitor two ormore grant channels. Moreover, by efficiently assigning grant channelsto each mobile station to monitor, and by efficiently selecting a grantchannel (from the assigned grant channels) to carry the notification toeach scheduled mobile station, the expected performance loss can befurther reduced.

[0022] In the following descriptions, the assignment of grant channelsto each mobile station to monitor is referred to as a “static”assignment because this assignment is typically performed only once atinitialization or at a similar initiation period of the mobile station.The selection of a grant channel from the statically assigned grantchannels is referred to as a “dynamic” assignment because this selectioncan be repeated at every time slot, and can select a different grantchannel.

[0023]FIG. 1 illustrates an exemplary configuration of assigning grantchannels to mobile stations in a CDMA system. The exemplaryconfiguration includes four individual grant channels GCH1, GCH2, GCH3,and GCH4; and seven mobile stations MS1, MS2, MS3, MS4, MS5, MS6, andMS7. Each mobile station monitors exactly two grant channels to receivethe notification of the grant. The grant notifications for GCH1 throughGCH4 all come from the base station. In the illustrated configuration,the first mobile station MS1 monitors grant channels GCH2 and GCH4; themobile station MS2 monitors grant channels GCH3 and GCH4; the mobilestation MS3 monitors grant channels GCH3 and GCH4; the mobile stationMS4 monitors grant channels GCH1 and GCH2; the mobile station MS5monitors grant channels GCH2 and GCH4; the mobile station MS6 monitorsgrant channels GCH1 and GCH4; and the mobile station MS7 monitors grantchannels GCH1 and GCH3. In FIG. 1, the grant channels monitored by eachmobile station are indicated by connecting lines leading from the mobilestation to the monitored grant channels from the base station.

[0024] In the FIG. 1 exemplary configuration, the base station canschedule mobile stations MS1, MS2, and MS5 in a particular time slot bysending grants for mobile station MS1 on grant channel GCH4; for mobilestation MS2 on grant channel GCH3; and for mobile station MS5 on grantchannel GCH2. The connecting lines corresponding to this schedulemapping are shown as dotted lines in FIG. 1. Since the base station isable to allocate a grant channel for each of the three mobile stations,there is no GCH outage in this schedule mapping. However, if the basestation were to schedule mobile station MS3 also in the same time slot,then a GCH outage would occur because there is no mapping for theexemplary configuration that could allocate a grant channel for each ofthe four scheduled mobile stations MS1, MS2, MS3, and MS5 in this case.That is, in the FIG. 1 configuration, only three grant channels GCH2,GCH3, and GCH4 are monitored among the four mobile stations MS1, MS2,MS3, and MS5. Thus, in this proposed schedule mapping, the GCH outageoccurs because of less than efficient assignment of grant channels tomobile stations.

[0025] In recognition of the above-described desirability of efficientlyassigning grant channels to each mobile station to monitor, and ofselecting a grant channel to carry the notification to each scheduledmobile station, this disclosure describes exemplary embodiments of suchassignments and/or selections. In particular, techniques for “dynamic”and “static” assignments are described in detail below. However, itshould be understood that even an “efficient” assignment of the grantchannels can sometimes result in a “GCH” outage because of systemresource limitations.

[0026]FIG. 2A, FIG. 2B, and FIG. 2C illustrate an exemplary “dynamic”process in which a grant channel is selected or assigned to carry agrant message to a scheduled mobile station. In the exemplary “dynamic”selection process, it is assumed that a number of grant channels, whichis less than the total number of individual grant channels, has beenassigned to each mobile station to monitor in a “static” assignmentprocess. Assumptions made about the static assignment process arefurther described in detail below.

[0027] Let k be the total number of individual grant channels. Thisnumber k is also the maximum number of mobile stations that can bescheduled simultaneously. Typically, k is between 2 and 8. Also, let/bethe number of grant channels assigned to each mobile station to monitor.

[0028] In one embodiment, a set of r mobile stations is scheduled ineach time slot (e.g. a period of 5 milliseconds), where r may differfrom time slot to time slot. The size of the set of mobile stations, r,can be assumed to be uniformly distributed over {1, 2, . . . , k}, i.e.,P(r)=1/k, r=1, . . . , k, or to be distributed according to thefollowing probability distribution: P(r=0), P(r=1), . . . ,P(r=8)={0.00860689, 0.0458367, 0.172538, 0.303443, 0.269816, 0.138511,0.0490392, 0.0104083, 0.00180144}. The latter probability distributionis based on separate reverse link system level simulation results, whichwere obtained by assuming ten full buffer FTP users in the sector.Moreover, a randomly selected set of grant channels {GCH₁, GCH₂, . . . ,GCH_(l)} is assigned to each mobile station to monitor.

[0029] In various embodiments and system configurations, the assignmentof grant channels to be monitored by the mobile station can be eitheractively managed by the base station or can be hashed, in which grantchannels are pseudo-randomly assigned based on a predeterminedtechnique.

[0030] As discussed above, when each mobile station monitors fewer thanthe total number of individual grant channels (i.e., l<k), it isdesirable for the base station to efficiently assign the grant channelin each time slot to a particular mobile station. This “dynamic”assignment task can be performed by searching for a solution in whichthe number of scheduled mobile stations that can be successfullyassigned to a grant channel (designated as r′) is maximal.

[0031] In various embodiments, the “dynamic” assignment can employ anexhaustive search by checking all l′ possible assignments. The searchcould be terminated earlier whenever an assignment is found which givesr′=r. For example, with l=3 and k=r=8, the length of the worst-caseexhaustive search would be 3⁸=6561.

[0032] Another way of carrying out an exhaustive search is to employ arecursive method. In this method, the search is performed in successiveattempts. In each attempt, the first available grant channel from thelist of l monitored grant channels is assigned to each mobile station.The assignment is performed sequentially for the r mobile stationsaccording to a listing or ordering of the mobile stations. When a mobilestation cannot be assigned a grant channel because all of its monitoredgrant channels have been previously assigned to other mobile stations bythe technique, then the technique backtracks (i.e., sequentiallyretraces the ordering of the mobile stations in the opposite direction)until a mobile station with at least one monitored but yet unassignedgrant channel is found. The assignment for that mobile station isswitched to the next available monitored grant channel. The assignmentprocess is then reattempted (i.e., the technique sequentially traces theordering of the mobile stations in the original direction) for theremaining mobile station(s). This forward-backward search is continueduntil an assignment that gives r′=r is found, or until all possibilitiesare exhausted. This recursive method is typically completed in fewerthan l^(r) operations but that number might be considered too lengthyfor many practical implementations.

[0033] In other embodiments, the “dynamic” assignment can employ arelatively short search (sometimes referred to as the “greedy”technique). In this short search, the first available grant channel fromthe list of/monitored grant channels is assigned to each mobile station.The assignment is done sequentially for the r mobile stations accordingto a listing or ordering of the mobile stations. Thus, this assignmentwill attempt to assign grant channels to mobile stations l×r times insuch a way that the list of mobile stations and/or the list of monitoredgrant channels for each mobile station is rotated, or rearranged,between attempts. For the example where l=3 and k=r=8, there will onlybe 3×8=24 assignments to check in the worst-case scenario, which is asignificantly smaller number than the worst-case exhaustive search equalto 3⁸=6561.

[0034] In the exemplary dynamic selection process illustrated in FIG.2A, FIG. 2B, and FIG. 2C, there are eight grant channels (k=8), GCH1through GCH8, and each mobile station monitors three grant channel(l=3). Furthermore, the base station schedules eight mobile stations(r=8) in a particular time slot. There are ten mobile stations, MS1through MS 10, operating within the operating boundary of the basestation.

[0035]FIG. 2A shows a “static” assignment of the grant channels to bemonitored for each mobile station. For example, mobile station MS1 isassigned to monitor grant channels GCH1, GCH2, and GCH3, and mobilestation MS2 is assigned to monitor grant channels GCH4, GCH5, and GCH6.The assignment of grant channels to monitor are also tabulated for theother mobile stations MS3 through MS10.

[0036]FIG. 2B shows a plurality of sequences of possible assignments formobile stations that are scheduled in a particular time slot to benotified about the grant. For example, R0 is the first sequence, R1 isthe second sequence, and so forth. Thus, in the first possible sequenceor iteration for the exemplary time slot of FIG. 2B, mobile stationsMS2, MS3, MS4, MS6, MS7, MS8, MS9, and MS10 are initially scheduled, asshown in the R0 row of FIG. 2B. It should be noted that the initialassignment ordering of MS2, MS3, . . . , MS10 is an arbitrary defaultordering selected for purposes of this example. Other initial assignmentorderings can be used, depending on system requirements or designpreferences. In this example, the mobile stations MS1 and MS5 are notscheduled. The second possible assignment sequence for mobile stationsand grant channels is shown in the R1 row of FIG. 2B as comprising thesequence MS3, MS4, MS6, MS7, MS8, MS9, MS10, and MS2. Again, MS1 and MS5are not scheduled.

[0037]FIG. 2C illustrates the “dynamic” assignment process using the“greedy” technique described above. For example, using the assignment ofgrant channels to mobile stations tabulated in FIG. 2A and the list ofmobile stations (R0) scheduled in the time slot as shown in FIG. 2B, thebase station attempts to assign a mobile station to each grant channel,GCH1 to GCH8. The first assignment attempt using the list R0 of FIG. 2Bis shown in the FIG. 2C column labeled R0.

[0038] According to the “greedy” technique, the first mobile station tobe scheduled, MS2 (see FIG. 2B, row R0), is assigned to the first grantchannel that MS2 is monitoring. Since FIG. 2A indicates that MS2 ismonitoring grant channels GCH4, GCH5, and GCH6, mobile station MS2 isassigned to the first of these, grant channel GCH4. The second mobilestation to be scheduled, MS3, monitors grant channels GCH1, GCH7, andGCH8. Thus, mobile station MS3 is assigned to grant channel GCH1, sinceGCH1 has not been previously assigned. The third mobile station to bescheduled, MS4, monitors grant channels GCH2, GCH3, and GCH4. Thus,mobile station MS4 is assigned to grant channel GCH2. By assigning theother mobile stations in similar processes, the assignment of mobilestations to grant channels can result as shown in the column of FIG. 2Clabeled as R0. This represents the assignment of mobile stations togrant channels using the first sequence R0 of mobile stations.Therefore, the FIG. 2C result indicates that mobile station MS3 isassigned to grant channel GCH1, mobile station MS4 is assigned to grantchannel GCH2, mobile station MS7 is assigned to grant channel GCH3,mobile station MS2 is assigned to grant channel GCH4, mobile stationMS10 is assigned to grant channel GCH5, mobile station MS8 is assignedto grant channel GCH6, and mobile station MS6 is assigned to grantchannel GCH8. However, the result also indicates that mobile station MS9cannot be scheduled in this time slot, because all available grantchannels have already been assigned, which results in a “GCH outage”.

[0039] Referring again to FIG. 2B, the scheduled mobile stations in theR0 sequence is rotated by one to produce the next assignment sequence,R1. The R1 row of FIG. 2B shows the sequence of the scheduled mobilestations as MS3, MS4, MS6, MS7, MS8, MS9, MS10, and MS2. Applying the“greedy” technique to this sequence, the first mobile station to bescheduled in R1, MS3, is assigned to the first grant channel that MS3 ismonitoring, GCH1 (see FIG. 2A). By assigning the other mobile stationsin similar processes, the assignment of mobile stations to grantchannels can result as shown in the R1 column of FIG. 2C. Therefore, theresult indicates that mobile station MS3 is assigned to grant channelGCH1, mobile station MS4 is assigned to grant channel GCH2, mobilestation MS7 is assigned to grant channel GCH3, mobile station MS10 isassigned to grant channel GCH4, mobile station MS2 is assigned to grantchannel GCH5, mobile station MS8 is assigned to grant channel GCH6, andmobile station MS6 is assigned to grant channel GCH8. However, theresult also indicates that once again the mobile station MS9 cannot bescheduled in this time slot, which again results in a “GCH outage”.

[0040] The above-described sequence for rotation of the scheduled mobilestations can be repeated until the number of scheduled mobile stationsthat can be successfully assigned to a grant channel (r′) is maximal, oruntil r′ is equal to the total number of scheduled mobile stations(r′=r′). When r′=r, there will be no “GCH outage”.

[0041] The loss in reverse link efficiency due to GCH outage can beestimated as follows. Let r be the total number of mobile stationsscheduled in a time slot. Assume that out of the r mobile stations, onlyr′ can be notified by using the grant channels. Then, the remaining r−r′mobile stations are in GCH outages. The efficiency in the time slot canbe computed as${1 - \frac{r - r^{\prime}}{r}} = {\frac{r^{\prime}}{r}.}$

[0042] This efficiency value is conservative because the loss due to GCHoutage can be mitigated by any or all of the following methods. Forexample, if there are mobile stations that cannot be notified due to GCHoutage, then other mobile stations with outstanding requests could stillbe scheduled in the same time slot. The r−r′ mobile stations that cannotbe notified due to GCH outage can be selected from the lower priorityusers (among the scheduled users). The r−r′ mobile stations that cannotbe notified due to GCH outage could be still scheduled on a common grantchannel.

[0043] Referring again to FIG. 2B, next consider the sequence ofscheduled mobile stations that is rotated to produce the sequence shownin row R4. The row R4 of FIG. 2B shows the sequence of the scheduledmobile stations as MS7, MS8, MS9, MS10, MS2, MS3, MS4, and MS6. Applyingthe “greedy” technique to this sequence, the first mobile station to bescheduled in this sequence, MS7, is assigned to the first grant channelthat MS7 is monitoring, GCH3. By assigning the other mobile stations insimilar processes, the assignment of mobile stations to grant channelscan result as shown in the column of FIG. 2C labeled as R4. Therefore,the result indicates that mobile station MS9 is assigned to grantchannel GCH1, mobile station MS4 is assigned to grant channel GCH2,mobile station MS7 is assigned to grant channel GCH3, mobile stationMS10 is assigned to grant channel GCH4, mobile station MS2 is assignedto grant channel GCH5, mobile station MS8 is assigned to grant channelGCH6, mobile station MS3 is assigned to grant channel GCH7, and mobilestation MS6 is assigned to grant channel GCH8. Accordingly, each of theeight scheduled mobile stations have been assigned to a grant channel,resulting in no “GCH outage”, as indicated in FIG. 2C.

[0044] The “greedy” technique applied in the exemplary dynamic selectionprocess, described in FIG. 2A, FIG. 2B, and FIG. 2C, is summarized inFIG. 3. The technique involves sequencing through a plurality ofsequences of scheduled mobile stations for a time slot. In oneembodiment, a first available (unassigned) grant channel from a list ofgrant channels monitored by a current mobile station is assigned to thecurrent mobile station (see box 300). In another embodiment, anyunassigned grant channel from the list of grant channels is assigned tothe current mobile station.

[0045] If it is determined that there are more mobile stations toprocess in the sequence of scheduled mobile stations (a “YES” outcome atbox 302), then the processing moves to a next mobile station in thesequence of scheduled mobile stations, at box 304, and repeats theprocess shown in box 300. Once the grant channel is assigned, that grantchannel is removed from the list of all available grant channels.Otherwise, if it is determined that there are no more mobile stations toprocess in the sequence of scheduled mobile stations (a “NO” outcome atbox 302), then a determination is made as to whether every grant channelhas been assigned a mobile station, at box 306. A “YES” outcome of thisdetermination will indicate that there is no GCH outage in schedulingthe grant channels, while a “NO” outcome will indicate that there is aGCH outage and that a new assignment should be attempted. Thus, if a GCHoutage is detected, at box 306, the sequence of the sequence ofscheduled mobile stations and/or the list of monitored grant channelsfor each mobile station is rearranged, at box 308. In one embodiment,the sequence of scheduled mobile stations and/or monitored grantchannels is rearranged in such a way that the sequence of mobilestations is rotated as shown in FIG. 2B. For example, in FIG. 2B,sequence R1 is a rotated version of sequence R0. In another embodiment,the sequence of the list of scheduled mobile stations and/or monitoredgrant channels is rearranged in any manner such that the new sequence isdifferent from the previous sequences.

[0046] If the GCH outage is detected, at box 306, the proceduresdescribed in boxes 300 and 304 are repeated, after rearrangement of thesequence of the list of scheduled mobile stations and/or monitored grantchannels. If the GCH outage persists until the rearrangement of thesequence has been exhausted and there are no more previously unassignedsequence, then the mobile station cannot be notified about the grant atthis time slot. In this case, the base station can wait until the nexttime slot to again attempt to schedule the mobile station affected bythe GCH outage.

[0047]FIG. 4 and FIG. 5 illustrate simulation results of exemplary grantchannel assignment performance expressed in terms of a relative reverselink efficiency for different number of grant channels (l) monitored byeach mobile station. Relative reverse link efficiency of 1.0 would beobtained if GCH outage never occurred. Each figure includes seven curvesrepresenting different total number of available grant channels (k).FIG. 4 illustrates the reverse link efficiency assuming the number ofmobile stations scheduled per time slot to be uniformly distributed over{1, 2, . . . , k}, i.e., P(r)=1/k, r=1, . . . , k. FIG. 5 illustratesthe reverse link efficiency assuming the number of mobile stationsscheduled per time slot to be distributed according to the followingprobability distribution: P(r=0), P(r=1), . . . , P(r=8)={0.00860689,0.0458367, 0.172538, 0.303443, 0.269816, 0.138511, 0.0490392, 0.0104083,0.00180144}.

[0048] Since the relative efficiency values shown in FIG. 4 and FIG. 5are normalized for each curve, efficiency value comparisons should notbe made between curves. That is, the curves do not provide insight intothe performance difference between cases corresponding to differentvalues of k. However, the curves do give insight into the performancedifference between cases corresponding to different l values for anygiven k. It should be understood that conservative assumptions were usedin computing the reverse link efficiency loss illustrated in FIG. 4 andFIG. 5. Thus, results shown herein should be construed as lower boundson performance.

[0049] The simulation results shown in FIG. 4 and FIG. 5 indicate thatwith each mobile station monitoring two grant channels (i.e., l=2),there is only an approximately 3% to 5% loss in efficiency (i.e., therelative efficiency is approximately 95% to 97%). When each mobilestation monitors at least three grant channels (i.e., l≧3), theefficiency loss is shown to be insignificant. Thus, the results showthat by having each mobile station monitor two or three individual grantchannels, the reverse link performance can be expected to approach theperformance achieved by having each mobile station to monitor all grantchannels. It should be noted that for randomly chosen assignment, themore appropriate performance measure, in some instances, is theprobability that the assignment gives the number of GCH outages which isless or equal to a given level is greater than a certain critical value.

[0050] Based on above results of the grant channel assignments,following assumptions would ensure adequate performance of the cdma2000reverse link. It is assumed that the mobile station has the capabilityto monitor at least two individual grant channels simultaneously. It isalso assumed that the base station has a capability to signal GCHassignment parameters to the mobile station in Layer 3 (L3) messages,such as enhanced channel assignment messages (ECAM) and universalhandoff direction messages (UHDM). The cdma2000 reverse link isdescribed in the document entitled “cdma2000 Reverse Link Proposal Rev.D”, document no. C30-20030217-011, which was proposed to a standardssetting committee of 3GPP2 on Feb. 17, 2003.

[0051] The simulation results illustrating expected performance loss dueto GCH outage were discussed above. However, these results were obtainedby simulation under the assumption that each mobile station has arandomly selected set of grant channels assigned to it (i.e., random“static” assignment). Various embodiments are described below, which usea nonrandom set of grant channels. It can be shown that using explicitlyassigned set of grant channels for each mobile station provides a betterperformance than using the random set. Moreover, for the uniformprobability distribution of the size of set of mobile stations scheduledin each time slot (i.e., uniformly distributed over {1, 2, . . . , k}),it can be shown that the reverse link efficiency of using the nonrandomset of grant channels is substantially optimal. That is, thebelow-described technique for non-randomly assigning sets of grantchannels to mobile stations provides maximum reverse link efficiency.

[0052] Let the total number of mobile stations (n) be ten (i.e., n=10),the number of grant channels (l) assigned to each mobile station tomonitor be one (i.e., l=1), and the number of grant channels (k) thatcan be scheduled simultaneously be eight (i.e., k=8). The mobilestations are designated from MS1 to MS10, while the grant channels aredesignated from GCH1 to GCH8. Furthermore, assume that the size of setof mobile stations scheduled in each time slot is uniformly distributed.Then, for substantially optimum assignment that gives the maximumefficiency, the efficiency is not less than $\begin{matrix}{{{c\left( {n,k} \right)} = {1 - {\sum\limits_{r = 0}^{k}\quad {{P(r)}\frac{\begin{pmatrix}{n - 2} \\{r - 2}\end{pmatrix} + \begin{pmatrix}{n - 3} \\{r - 2}\end{pmatrix} + \begin{pmatrix}{n - 4} \\{r - 3}\end{pmatrix} + \begin{pmatrix}{n - 4} \\{r - 4}\end{pmatrix}}{r \cdot \begin{pmatrix}n \\r\end{pmatrix}}}}}},} & (1)\end{matrix}$

[0053] where $\begin{matrix}\begin{matrix}{\frac{\begin{pmatrix}{n - 2} \\{r - 2}\end{pmatrix} + \begin{pmatrix}{n - 3} \\{r - 2}\end{pmatrix} + \begin{pmatrix}{n - 4} \\{r - 3}\end{pmatrix} + \begin{pmatrix}{n - 4} \\{r - 4}\end{pmatrix}}{r \cdot \begin{pmatrix}n \\r\end{pmatrix}}\hat{=}\left\{ {\begin{matrix}0 & {{{if}\quad r} = 0} \\1 & {{{if}\quad r} = 1}\end{matrix},} \right.} \\{{\begin{pmatrix}y \\x\end{pmatrix} = 0},{{{if}\quad x} < 0},\quad {\begin{pmatrix}y \\x\end{pmatrix} = 1},{{{if}\quad x} = 0},{and}}\end{matrix} & (2)\end{matrix}$

[0054] P(r) is the probability distribution of the set size for the setof mobile stations that is scheduled in a time slot.

[0055] In one exemplary embodiment of a non-random “static” assignment,a number of assumptions is made as described above, including theassumption that the size of set of mobile stations scheduled in eachtime slot is uniformly distributed as P(r)=1/k, r=1, . . . , k. In thisexemplary embodiment, the maximum reverse link efficiency can beachieved by assigning grant channels GCH1, GCH2, GCH3, GCH4, GCH5, GCH6,GCH7, GCH8, GCH1, and GCH2 to scheduled mobile stations MS1, MS2, MS3,MS4, MS5, MS6, MS7, MS8, MS9, and MS10, respectively.

[0056] To verify and prove that the maximum reverse link efficiency canbe achieved by assigning the grant channels to the scheduled mobilestations, as defined above, consider the following. For n=10 mobilestations, k=8 scheduled grant channels, and l=1 grant channels assignedto each mobile station to monitor, the number 1 grant channel (referredto as a-number 1) is assigned to mobile stations MS1 and MS9, anda-number 2 is assigned to mobile stations MS2 and MS10. Moreover, grantchannel a-number i, where i=3, 4, 5, 6, 7, 8, is assigned to the mobilestation MS i.

[0057] A combination of r different mobile stations, by definition,results in the GCH outage if it contains mobile stations with the samea-numbers. From a combinatorial point of view, the unorderedcombinations are considered here. Also, the outage of a combination hasthe multiplicity m, where m≦k−1, if the number of different a-numbers inthe combination is k−m. The combination of r mobile stations is the setof mobile stations scheduled in a time slot.

[0058] The number of combinations that results in the GCH outages, U, iscalculated below. The outage occurs in three cases, where${\begin{pmatrix}y \\x\end{pmatrix} = 0},$

[0059] if x<0 and ${\begin{pmatrix}y \\x\end{pmatrix} = 1},{{{if}\quad x} = 0.}$

[0060] In the first case, mobile stations MS1 and MS9 are in combinationand mobile station MS10 is not. The number of such differentcombinations is $\begin{pmatrix}{n - 3} \\{r - 2}\end{pmatrix}.$

[0061] In this case, the 2 in r-2 is the number of mobile stations(i.e., MS1 and MS9) that must participate in all such combinations. Theother r-2 mobile stations in such combinations are taken from the n-3mobile stations MS2, MS3, MS4, MS5, MS6, MS7, and MS8.

[0062] In the second case, mobile stations MS2 and MS10 are incombination without any additional restriction. The number of suchdifferent combinations is $\begin{pmatrix}{n - 2} \\{r - 2}\end{pmatrix}.$

[0063] In this case, the 2 in r-2 refers to mobile stations MS2 and MS10that must participate in all such combinations. The other r-2 mobilestations in such combinations are taken from the n-2 mobile stationsMS1, MS3, MS4, MS5, MS6, MS7, MS8, and MS9.

[0064] In the third case, mobile stations MS1, MS9, and MS10 are incombination and mobile station MS2 is not. The number of such differentcombinations is $\begin{pmatrix}{n - 4} \\{r - 3}\end{pmatrix}.$

[0065] In this case, the 3 in r-3 refers to mobile stations MS1, MS9,and MS10 that must participate in all such combinations. The other r-3mobile stations in such combinations are taken from the n-4 mobilestations MS3, MS4, MS5, MS6, MS7, and MS8.

[0066] The combinations in the three cases considered above aredifferent. Thus, $\begin{matrix}{U = {\begin{pmatrix}{n - 2} \\{r - 2}\end{pmatrix} + \begin{pmatrix}{n - 3} \\{r - 2}\end{pmatrix} + {\begin{pmatrix}{n - 4} \\{r - 3}\end{pmatrix}.}}} & (3)\end{matrix}$

[0067] The number of combinations with the outages of multiplicity two,U₂, is then calculated as follows: $\begin{matrix}{U_{2} = {\begin{pmatrix}{n - 4} \\{r - 4}\end{pmatrix}.}} & (4)\end{matrix}$

[0068] Thus, the formulation of Equation (4) indicates that eachcombination with the outage of multiplicity two should contain themobile stations MS1, MS2, MS9, and MS10 and the other r-4 mobilestations in such combinations are taken from the n-4 mobile stationsMS3, MS4, MS5, MS6, MS7, and MS8.

[0069] For the assignment considered above, the combinations with theoutage of multiplicity greater than two do not exist. Hence, Equations(3) and (4) for expressions U and U₂ provide the following generalexpression for U₁, number of combinations that give the outages ofmultiplicity one: $\begin{matrix}{U_{1} = {\begin{pmatrix}{n - 2} \\{r - 2}\end{pmatrix} + \begin{pmatrix}{n - 3} \\{r - 2}\end{pmatrix} + \begin{pmatrix}{n - 4} \\{r - 3}\end{pmatrix} - {\begin{pmatrix}{n - 4} \\{r - 4}\end{pmatrix}.}}} & (5)\end{matrix}$

[0070] The total number of combination of n mobile stations taken r at atime is given as $\begin{pmatrix}n \\r\end{pmatrix}.$

[0071] If a combination is without an outage, then all r mobile stationsin the combination can be notified by using the grant channels. If acombination is with an outage of multiplicity one, then one mobilestation in the combination cannot use the grant channels. If acombination is with an outage of multiplicity two, then two mobilestations in the combination cannot use the grant channels.

[0072] If all $\quad\begin{pmatrix}n \\r\end{pmatrix}$

[0073] combinations have the same probability of appearing, then theaverage number of mobile stations that are notified is $\begin{matrix}{{{b(r)} = {{{\frac{U_{0}}{\begin{pmatrix}n \\r\end{pmatrix}}r} + {\frac{U_{1}}{\begin{pmatrix}n \\r\end{pmatrix}}\left( {r - 1} \right)} + {\frac{U_{2}}{\begin{pmatrix}n \\r\end{pmatrix}}\left( {r - 2} \right)}} = {r - \frac{U_{1}}{\begin{pmatrix}n \\r\end{pmatrix}} - \frac{2U_{2}}{\begin{pmatrix}n \\r\end{pmatrix}}}}},} & (6)\end{matrix}$

[0074] where $U_{0} = {\begin{pmatrix}n \\r\end{pmatrix} - U_{1} - U_{2}}$

[0075] is the number of combinations without outages and b(0)=0. Let rbe a random variable having the distribution P(r).

[0076] The normalized-with-respect-to-r average number of mobilestations that are notified is $\begin{matrix}\begin{matrix}{{{a(r)} = \frac{b(r)}{r}},} & {{{a(0)} = 0},} & {{a(1)} = 1.}\end{matrix} & (7)\end{matrix}$

[0077] The efficiency c(n, k) is defined by $\begin{matrix}{{c\left( {n,k} \right)}\hat{=}{\sum\limits_{r = 0}^{k}{{P(r)}{{a(r)}.}}}} & (8)\end{matrix}$

[0078] Using Equation (4) through Equation (7), Equation (1) is obtainedfor the assignment of grant channels GCH1, GCH2, GCH3, GCH4, GCH5, GCH6,GCH7, GCH8, GCH1, GCH2 to mobile stations MS1, MS2, MS3, MS4, MS5, MS6,MS7, MS8, MS9, and MS10, respectively.

[0079] For the uniform distribution P(r)=1/k, r=1, . . . , k, theassignment of the above-listed grant channels to the mobile stations isshown to be substantially optimal because c(n, k) is same for anyassignment such that of the ten a-numbers, eight have differenta-numbers and two have additional different a-numbers taken from thoseeight a-numbers. For any assignment with less than eight differenta-numbers or with the different eight a-numbers, but with identical twoadditional a-numbers, c(n, k) is less than c(n, k) computed fromEquation (8).

[0080] In one example, consider the case where n=10, k=8, and P(r)=1/k,r=1, . . . , k. Then, according to Equation (8), c(n, k)=0.922 whengrant channels GCH1, GCH2, GCH3, GCH4, GCH5, GCH6, GCH7, GCH8, GCH1,GCH2 are optimally assigned to mobile stations MS1, MS2, MS3, MS4, MS5,MS6, MS7, MS8, MS9, and MS10, respectively. However, for the same casebut with a randomly selected assignment, the efficiency is shown to beabout 0.82 (see FIG. 4).

[0081] In another example, consider the case where n=10, k=8, and theprobability distribution is as follows: P(0)=0.00860689, P(1)=0.0458367,P(2)=0.172538, P(3)=0.303443, P(4)=0.269816, P(5)=0.138511,P(6)=0.0490392, P(7)=0.0104083, P(8)=0.00180144. Then, according toEquation (8), c(n, k)=0.937 when grant channels GCH1, GCH2, GCH3, GCH4,GCH5, GCH6, GCH7, GCH8, GCH1, GCH2 are optimally assigned to mobilestations MS1, MS2, MS3, MS4, MS5, MS6, MS7, MS8, MS9, and MS10,respectively. However, for the same case but with a randomly selectedassignment, the efficiency is shown to be about 0.86 (see FIG. 5).

[0082] Accordingly, it can be seen that the non-random assignment ofgrant channels to mobile stations provides higher reverse linkefficiency than the random assignment.

[0083] In another exemplary embodiment of a non-random “static”assignment, a number of assumptions is made as described below. Let thetotal number of mobile stations (n) be an even number, the number ofgrant channels (l) assigned to each mobile station to monitor be one(i.e., l=1), and the number of grant channels (k) that can be scheduledsimultaneously be k=n/2. The mobile stations are designated from MS1 toMSn, while the grant channels are designated from GCH1 to GCHk.Furthermore, assume that the size of set of mobile stations scheduled ineach time slot is uniformly distributed. Then, for substantially optimumassignment that gives the maximum efficiency, the efficiency is not lessthan $\begin{matrix}{{{c\left( {n,k} \right)} = {1 - {\sum\limits_{r = 1}^{k}{{P(r)}\frac{\sum\limits_{i = 1}^{\lfloor{k/2}\rfloor}{{i \cdot \begin{pmatrix}{n/2} \\i\end{pmatrix}}{\begin{pmatrix}{\left( {n/2} \right) - i} \\{r - {2i}}\end{pmatrix} \cdot 2^{r - {2i}}}}}{r \cdot \begin{pmatrix}n \\r\end{pmatrix}}}}}},} & (9)\end{matrix}$

[0084] where $\begin{matrix}{{\begin{pmatrix}y \\x\end{pmatrix} = 0},{{{if}\quad x} < 0},} & {{\begin{pmatrix}y \\x\end{pmatrix} = 1},{{{if}\quad x} = 0},}\end{matrix}$

[0085] P(r) is the probability distribution of the set size for the setof mobile stations that is scheduled in a time slot.

[0086] In this exemplary embodiment, the maximum reverse link efficiencycan be achieved by assigning grant channels GCH1, GCH2, . . . ,GCH(n/2), GCH1, GCH2, . . . , and GCH(n/2) to scheduled mobile stationsMS1, MS2, . . . , and MSn, respectively.

[0087] To verify and prove that the maximum reverse link efficiency canbe achieved by assigning the grant channels to the scheduled mobilestations, as defined above, consider the following. For a given totaleven number of mobile stations n and a given number of grant channelsthat can be scheduled simultaneously k=n/2, let U(n, k, r, m) denote thenumber of combinations having r different mobile stations and GCH outageof multiplicity m. Let S(n, k, r, m) denote the set of these U(n, k, r,m) combinations. In this proof, the definitions of the combination,a-number, outage, and outage of multiplicity m are kept same as thedefinitions in the first embodiment described above.

[0088] For 0≦r<2m,

U(n, k, r, m)=0.  (10)

[0089] For 2 m≦r≦k, $\begin{matrix}{{U\left( {n,k,r,m} \right)} = {\begin{pmatrix}{n/2} \\m\end{pmatrix}{\begin{pmatrix}{\left( {n/2} \right) - m} \\{r - {2m}}\end{pmatrix} \cdot {2^{r - {2m}}.}}}} & (11)\end{matrix}$

[0090] Equation (11) can be validated as follows. Each combination fromS(n, k, r, m) has exactly m pair of mobile stations such that the mobilestations from each pair have the identical a-numbers. The number of suchdifferent m pairs is equal to $\begin{pmatrix}{n/2} \\m\end{pmatrix}.$

[0091] The m pairs are sometimes referred to as twins pairs. For eachcombination from S(n, k, r, m), there is a set of the rest pairs (i.e.,the pairs that are not among the m twins pairs). The number of the restpairs is equal to (n/2)−m.

[0092] A pair from the rest pairs can give no more than one of itsmobile stations to the combination. The combination can get exactly r-2msuch mobile stations from the rest pairs, which means that for the giventwins pairs and given r-2m pairs from the rest pairs, the rest pairs canprovide 2^(r-2m) different mobile station combinations. For the giventwins pairs, the total number of different sets of the r-2m rest pairsis $\begin{pmatrix}{\left( {n/2} \right) - m} \\{r - {2m}}\end{pmatrix},$

[0093] which is given in Equation (11).

[0094] The total number of combination of n mobile stations taken r at atime is $\begin{pmatrix}n \\r\end{pmatrix}.$

[0095] Thus, if all $\begin{pmatrix}n \\r\end{pmatrix}\quad$

[0096] combinations have the same probability of appearing, then theaverage number of mobile stations that are notified is $\begin{matrix}{{b\left( {n,k,r} \right)} = {{\sum\limits_{m = 0}^{\lfloor{k/2}\rfloor}{\frac{U\left( {n,k,r,m} \right)}{\begin{pmatrix}n \\r\end{pmatrix}}\left( {r - m} \right)}} = {r - {\frac{1}{\begin{pmatrix}n \\r\end{pmatrix}}{\sum\limits_{m = 1}^{\lfloor{k/2}\rfloor}{{{mU}\left( {n,k,r,m} \right)}.}}}}}} & (12)\end{matrix}$

[0097] Equation (9) can be obtained after normalization of b(n, k, r)with respect to r and averaging over r.

[0098] In one example, consider the case where n=10, k=5, and P(r)=1/k,r=1, . . . , k. Then, according to Equation (9), c(n, k)=0.889 whengrant channels GCH1, GCH2, . . . , GCH(n/2), GCH1, GCH2, . . . , andGCH(n/2) are optimally assigned to scheduled mobile stations MS1, MS2, .. . , and MSn, respectively. However, for the same case but with arandomly selected assignment, the efficiency is shown to be about 0.83(see FIG. 4).

[0099] In another example with uniform probability distribution (i.e.,P(r)=1/k, r=1, . . . , k), consider the cases where [n=16, k=8], [n=14,k=7], and [n=12, k=6]. Again, according to Equation (9), c(n, k)=0.883,c(n, k)=0.885, and c(n, k)=0.886, respectively, when grant channelsGCH1, GCH2, . . . , GCH(n/2), GCH1, GCH2, . . . , and GCH(n/2) areoptimally assigned to scheduled mobile stations MS1, MS2, . . . , andMSn, respectively. The efficiency number is not given for the same casebut with a randomly selected assignment. However, the efficiency numberis expected to be lower than those given for the non-random case shownhere.

[0100]FIG. 6 is a flow chart that illustrates the above-describednon-random “static” assignment of sets of grant channels to mobilestations to monitor. The assignment process summarized in FIG. 6 assumesthat n represents the total number of mobile stations and that krepresents the total number of grant channels that can be scheduledsimultaneously. Thus, k must be at least as large as r, which is equalto the number of mobile stations that is scheduled in a time slot.

[0101] The non-random “static” assignment process successively assignsthe first k mobile stations of the total n mobile stations to the kgrant channels, respectively, at box 600. The next (n-k) mobile stationsare assigned to the first (n-k) grant channels, at box 602. Thus, thefirst (n-k) grant channels will have at least two mobile stationsassigned to them.

[0102]FIG. 7 is a simplified block diagram of a CDMA communicationsystem 700, such as the 1 xEV-DV access network. The system 700 includesat least a base station 750 and a mobile station 710 that are capable ofimplementing various aspects of the invention. For a particularcommunication, voice data, packet data, and/or messages may be exchangedbetween the base station 750 and the mobile station 710. Various typesof messages may be transmitted such as messages used to establish acommunication session between the base station and the mobile stationand messages used to control a data transmission (e.g., power control,data rate information, acknowledgment, and so on).

[0103] For the forward link, at the base station 750, voice and/orpacket data (e.g., from a data source 776) and messages (e.g., from thecontroller 764) are processed (e.g., formatted and encoded) by atransmit (TX) data processor 774, further processed (e.g., covered andspread) by a modulator (MOD) 772, and conditioned (e.g., converted toanalog signals, amplified, filtered, and quadrature modulated) by atransmitter unit (TMTR) 770 to generate a forward link signal.

[0104] The messages processed by the base station controller 764 mayinclude grant messages carrying grants specific to mobile stations, suchas R-ESCH grants. These messages may use individual Grant Channelsoptimally assigned according to the techniques described above. Thecontroller 764 schedules the mobile stations in a particular time slotby processing and assigning a grant channel to each scheduled mobilestation. The controller includes memory in which one maintained listsand orderings of the mobile stations, grant channels, and time slotconfigurations, such as assignments and scheduling, as illustrated inFIGS. 2A, 2B, 2C. In one embodiment, the controller 764 includes a grantchannel assignment module 780 that assigns to a current mobile stationof the plurality of scheduled mobile stations, a previously unassignedgrant channel from a list of grant channels monitored by the currentmobile station. The controller 764 may also include a rearrangementmodule 782 configured to rearrange the order of the plurality ofscheduled mobile stations and repeat the assignment process executed bythe grant channel assignment module, if not every grant channel has beenassigned a mobile station. The forward link signal is then routedthrough the duplexer 754 and transmitted via the antenna 752 to themobile station 710.

[0105] At the mobile station 710, the forward link signal is received bythe antenna 732, routed through the duplexer 730, and provided to areceiver unit 728. The receiver unit 728 conditions (e.g., downconverts,filters, amplifies, quadrature demodulates, and digitizes) the receivedsignal and provides samples. The samples are processed (e.g.,despreaded, decovered, and pilot demodulated) by a demodulator 726 toprovide symbols, and the symbols are further processed (e.g., decodedand checked) by a receive data processor 724 to recover the data andmessages transmitted on the forward link. The recovered data is providedto a data sink 722, and the recovered messages may be provided to thecontroller 720.

[0106] On the reverse link, at the mobile station 710, voice and/orpacket data (e.g., from a data source 712) and messages (e.g., from acontroller 720) are provided to a transmit (TX) data processor 714,which formats and encodes the data and messages with one or more codingschemes to generate coded data. Each coding scheme may include anycombination of cyclic redundancy check (CRC), convolutional, Turbo,block, and other coding, or no coding at all. Typically, voice data,packet data, and messages are coded using different schemes, anddifferent types of message may also be coded differently.

[0107] The coded data is then provided to a modulator (MOD) 716 andfurther processed (e.g., covered, spread with short PN sequences, andscrambled with a long PN sequence assigned to the user terminal). Themodulated data is then provided to a transmitter unit (TMTR) 718 andconditioned (e.g., converted to one or more analog signals, amplified,filtered, and quadrature modulated) to generate a reverse link signal.The reverse link signal is routed through a duplexer (D) 730 andtransmitted via an antenna 732 to the base station 750.

[0108] At the base station 750, the reverse link signal is received byan antenna 752, routed through a duplexer 754, and provided to areceiver unit (RCVR) 756. The receiver unit 756 conditions (e.g.,filters, amplifies, downconverts, and digitizes) the received signal andprovides samples. A demodulator (DEMOD) 758 receives and processes(e.g., despreads, decovers, and pilot demodulates) the samples toprovide recovered symbols. The demodulator 758 may implement a rakereceiver that processes multiple instances of the received signal andgenerates combined symbols. A receive (RX) data processor 760 thendecodes the symbols to recover the data and messages transmitted on thereverse link. The recovered voice/packet data is provided to a data sink762 and the recovered messages may be provided to a controller 764. Theprocessing by the demodulator 758 and the RX data processor 760 arecomplementary to that performed at the mobile station 710.

[0109] Those of skill in the art will understand that information andsignals may be represented using any of a variety of differenttechnologies and techniques. For example, data, instructions, commands,information, signals, bits, symbols, and chips that may be referencedthroughout the above description may be represented by voltages,currents, electromagnetic waves, magnetic fields or particles, opticalfields or particles, or any combination thereof.

[0110] Those of skill will further appreciate that the variousillustrative logical blocks, modules, circuits, and techniques describedin connection with the embodiments disclosed herein may be implementedas electronic hardware, computer software, or combinations of both. Toclearly illustrate this interchangeability of hardware and software,various illustrative components, blocks, modules, circuits, and stepshave been described above generally in terms of their functionality.Whether such functionality is implemented as hardware or softwaredepends upon the particular application and design constraints imposedon the overall system. Skilled artisans may implement the describedfunctionality in varying ways for each particular application, but suchimplementation decisions should not be interpreted as causing adeparture from the scope of the present invention.

[0111] The various illustrative logical blocks, modules, and circuitsdescribed in connection with the embodiments disclosed herein may beimplemented or performed with a general purpose processor, a digitalsignal processor (DSP), an application specific integrated circuit(ASIC), a field programmable gate array (FPGA) or other programmablelogic device, discrete gate or transistor logic, discrete hardwarecomponents, or any combination thereof designed to perform the functionsdescribed herein. A general purpose processor may be a microprocessor,but in the alternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

[0112] The procedures of a method or technique described in connectionwith the embodiments disclosed herein may be embodied directly inhardware, in a software module executed by a processor, or in acombination of the two. A software module may reside in RAM memory,flash memory, ROM memory, EPROM memory, EEPROM memory, registers, harddisk, a removable disk, a CD-ROM, or any other form of storage mediumknown in the art. An exemplary storage medium is coupled to theprocessor such that the processor can read information from, and writeinformation to, the storage medium. In the alternative, the storagemedium may be integral to the processor. The processor and the storagemedium may reside in an ASIC. The ASIC may reside in a user terminal. Inthe alternative, the processor and the storage medium may reside asdiscrete components in a user terminal.

[0113] The previous description of the disclosed embodiments is providedto enable any person skilled in the art to make or use the presentinvention. Various modifications to these embodiments will be readilyapparent to those skilled in the art, and the generic principles definedherein may be applied to other embodiments without departing from thespirit or scope of the invention. Thus, the present invention is notintended to be limited to the embodiments shown herein but is to beaccorded the widest scope consistent with the principles and novelfeatures disclosed herein.

What is claimed is:
 1. A method for scheduling grant channels to carrygrant messages to a plurality of scheduled mobile stations in an area ofa communications network, the method comprising: assigning to a currentmobile station in an ordering of the plurality of scheduled mobilestations, a previously unassigned grant channel from a list of grantchannels monitored by the current mobile station; and repeating theassignment for a next mobile station in the ordering of scheduled mobilestations, if there are more mobile stations to be processed in theordering of the scheduled mobile stations.
 2. The method of claim 1,further comprising: rearranging the ordering for the plurality ofscheduled mobile stations after the mobile stations in the ordering havebeen assigned grant channels, and repeatedly assigning grant channels tomobile stations, until every grant channel has been assigned a mobilestation in the ordering.
 3. The method of claim 2, wherein rearrangingthe ordering includes rearranging the order of the list of grantchannels monitored by the current mobile station.
 4. The method of claim2, wherein rearranging the ordering includes rotating the order of theplurality of scheduled mobile stations.
 5. The method of claim 1,wherein the previously unassigned grant channel includes a firstavailable grant channel from the list of grant channels monitored by thecurrent mobile station.
 6. The method of claim 1, wherein the pluralityof scheduled mobile stations is a subset of a total number of mobilestations operating within the area.
 7. A method for scheduling grantchannels to carry grant messages to a plurality of scheduled mobilestations in a sector of a communications network, the method comprising:assigning at least one grant channel to each scheduled mobile station inan ordering of the scheduled mobile stations for monitoring; assigningto a current mobile station in the ordering, a grant channel that ismonitored by the current mobile station and is not previously assignedto the current mobile station; changing the current mobile station to anext mobile station in the ordering of scheduled mobile stations, andrepeating the assigning of a previously unassigned monitored grantchannel, if there are more mobile stations to be processed in theordering of scheduled mobile stations.
 8. The method of claim 7, furthercomprising: rearranging the ordering for the plurality of scheduledmobile stations after the mobile stations in the ordering have beenassigned grant channels, and repeatedly assigning grant channels tomobile stations, until every grant channel has been assigned a mobilestation in the ordering.
 9. The method of claim 8, wherein assigning atleast one grant channel includes assigning a first plurality of mobilestations to every grant channel, in order.
 10. The method of claim 9,wherein the first plurality of mobile stations is a subset of a totalnumber of mobile stations operating within the sector.
 11. The method ofclaim 10, wherein assigning at least one grant channel further includesassigning remainder of mobile stations to a first same number of grantchannels in order.
 12. The method of claim 8, wherein assigning at leastone grant channel includes randomly selecting a set of grant channelsfrom the at least one grant channel to assign to each mobile station tomonitor.
 13. The method of claim 8, wherein the previously unassignedgrant channel includes a first available grant channel from the at leastone grant channel monitored by the current mobile station.
 14. Themethod of claim 13, wherein rearranging the order includes rearrangingthe order of the at least one grant channel monitored by the currentmobile station.
 15. The method of claim 8, wherein rearranging the orderincludes rotating the order of the plurality of scheduled mobilestations.
 16. The method of claim 8, wherein the plurality of scheduledmobile stations is a subset of a total number of mobile stationsoperating within the sector.
 17. A base station in a CDMA communicationsnetwork, the base station comprising: a controller configured toschedule grant channels to carry grant messages to a plurality ofscheduled mobile stations in an area of the CDMA communications network,the controller including a grant channel assignment module that operatesto: assign to a current mobile station in an ordering of the pluralityof scheduled mobile stations, a previously unassigned grant channel froma list of grant channels monitored by the current mobile station; andrepeat the assignment for a next mobile station in the ordering ofscheduled mobile stations, if there are more mobile stations to beprocessed in the ordering of the scheduled mobile stations; a modulatorconfigured to process and spread the grant messages; and a transmitterunit configured to condition the processed grant messages, to generate aforward link signal, and to transmit the forward link signal on grantchannels.
 18. The base station of claim 17, wherein each message in thegrant messages include messages specific to a mobile station.
 19. Thebase station of claim 17, wherein the grant messages include ReverseEnhanced Supplemental Channel (R-ESCH) grants.
 20. The base station ofclaim 17, wherein the controller includes: a rearrangement moduleconfigured to rearrange the order for the plurality of scheduled mobilestations, and to repeat the assignment process executed by the grantchannel assignment module, if not every grant channel has been assigneda mobile station, if not every grant channel has been assigned a mobilestation.
 21. The base station of claim 20, wherein the rearrangementmodule rearranges the order of the list of grant channels monitored bythe current mobile station.
 22. The base station of claim 21, whereinthe rearrangement module rearranges the list order by rotating the orderof the plurality of scheduled mobile stations.
 23. The base station ofclaim 17, wherein the previously unassigned grant channel includes afirst available grant channel from the list of grant channels monitoredby the current mobile station.
 24. The base station of claim 17, whereinthe plurality of scheduled mobile stations is a subset of a total numberof mobile stations operating within the area.
 25. A transceivercontroller in a CDMA communications network, the transceiver controllercomprising: a grant channel assignment module configured to assign grantchannels to carry grant messages to a current mobile station in anordering of a plurality of scheduled mobile stations in an area of theCDMA communications network, a previously unassigned grant channel froma list of grant channels monitored by the current mobile station, and torepeat the assignment for a next mobile station in the ordering ofscheduled mobile stations, if there are more mobile stations to beprocessed in the ordering of the scheduled mobile stations.
 26. Thetransceiver controller of claim 25, wherein each message in the grantmessages include messages specific to a mobile station.
 27. Thetransceiver controller of claim 25, wherein the grant messages includeReverse Enhanced Supplemental Channel (R-ESCH) grants.
 28. Thetransceiver controller of claim 25, wherein the grant channel assignmentmodule includes: a rearrangement module configured to rearrange theorder for the plurality of scheduled mobile stations, and to repeat theassignment process executed by the grant channel assignment module, ifnot every grant channel has been assigned a mobile station, if not everygrant channel has been assigned a mobile station.
 29. The transceivercontroller of claim 28, wherein the rearrangement module rearranges theorder of the list of grant channels monitored by the current mobilestation.
 30. The transceiver controller of claim 29, wherein therearrangement module rearranges the list order by rotating the order ofthe plurality of scheduled mobile stations.
 31. The transceivercontroller of claim 25, wherein the previously unassigned grant channelincludes a first available grant channel from the list of grant channelsmonitored by the current mobile station.
 32. The transceiver controllerof claim 25, wherein the plurality of scheduled mobile stations is asubset of a total number of mobile stations operating within the area.33. A CDMA communications network, comprising: a first plurality ofmobile stations operating within the CDMA communications network; and abase station, comprising: a controller configured to schedule grantchannels to carry grant messages to a plurality of scheduled mobilestations in an area of the CDMA communications network, the controllerincluding a grant channel assignment module that operates to assign to acurrent mobile station in an ordering of the plurality of scheduledmobile stations, a previously unassigned grant channel from a list ofgrant channels monitored by the current mobile station; and repeat theassignment for a next mobile station in the ordering of scheduled mobilestations, if there are more mobile stations to be processed in theordering of the scheduled mobile stations; a modulator configured toprocess and spread the grant messages; and a transmitter unit configuredto condition the processed grant messages, to generate a forward linksignal, and to transmit the forward link signal on grant channels. 34.The communications network of claim 33, wherein the controller in thebase station further includes: a rearrangement module configured torearrange the order for the plurality of scheduled mobile stations, andto repeat the assignment process executed by the grant channelassignment module, if not every grant channel has been assigned a mobilestation, if not every grant channel has been assigned a mobile station.35. The communications network of claim 34, wherein the rearrangementmodule rearranges the order of the list of grant channels monitored bythe current mobile station.
 36. The communications network of claim 35,wherein the rearrangement module rearranges the list order by rotatingthe order of the plurality of scheduled mobile stations.
 37. Thecommunications network of claim 33, wherein the previously unassignedgrant channel includes a first available grant channel from the list ofgrant channels monitored by the current mobile station.
 38. Thecommunications network of claim 33, wherein the plurality of scheduledmobile stations is a subset of a total number of mobile stationsoperating within the area.